1. Field of the Invention
The present invention relates to an image forming apparatus for detecting information regarding characteristics or a type of a sheet material on which an image is formed and controlling an image forming operation based on a detection result and to a control method of the image forming apparatus.
2. Description of the Related Art
As image forming apparatuses for forming an image based on an image signal, various systems such as electrophotographic system and ink-jet system are conventionally used. In such image forming apparatuses, at present, there are a variety of print sheets (sheet materials) as media to be printed. Media having various features such as size, transmittancy, and glossiness exist. From such a background, in order to obtain high image quality, it is necessary to optimally form images to various kinds of media.
The image forming apparatus of the electrophotographic system such as copying apparatus or laser printer has a latent image holding material, a developing apparatus, a transfer unit, and a fixing apparatus. The latent image holding material holds a latent image. The developing apparatus visualizes the held latent image as a developer image by applying a developer to the latent image holding material. The transfer unit transfers the developer image visualized by the developing apparatus onto the sheet material which is conveyed in a predetermined direction. The fixing apparatus fixes the developer image onto the sheet material by heating and pressurizing the sheet material on which the developer image has been transferred by the transfer unit under predetermined fixing processing conditions.
Hitherto, in the image forming apparatus, when the printing operation is executed, a size and a type (hereinbelow, also referred to as a sheet type) of the sheet material can be arbitrarily set by the user from an operation panel provided for a main body of the image forming apparatus or from a host computer connected to the image forming apparatus (hereinbelow, such a mode is referred to as a “designating mode”). According to the settings, for example, in the case of the foregoing image forming apparatus of the electrophotographic system, control to change an image forming condition such as developing condition, transfer condition, or fixing processing conditions (for example, a fixing temperature and a conveying speed of the sheet material which passes through the fixing apparatus) is made.
However, the user does not certainly make the setting of the sheet type mentioned above. Therefore, particularly, in an image forming apparatus for business use, a print mode adapted to automatically discriminate the sheet type and set the image forming conditions based on the detection result (hereinbelow, such a mode is referred to as an automatic mode) is prepared.
For example, Japanese Patent Application Laid-Open No. 2002-182518 and Japanese Patent Application Laid-Open No. 2003-302885 have presented the following apparatuses. There is an apparatus in which the sheet type is automatically discriminated by a method whereby a surface image of a stopped sheet material is photographed by a CMOS (Complementary Metal Oxide Semiconductor) sensor and a surface smoothness of the sheet material is detected, and the developing condition, transfer condition, or fixing condition is variably controlled according to a discrimination result. Further, an apparatus in which a light emitting source is arranged at a position which faces a sensor for automatically discriminating the sheet type and transmitted light is detected, thereby discriminating the sheet type based on the transmitted light (discriminating a thickness of sheet material) has also been proposed. By using such a sheet type discriminating method, control is made so as to perform the discrimination each time the sheet material is fed (control is made so as to automatically discriminate all of the sheet types) or control is made so as to perform the discrimination only about the first sheet of a print job and to omit the discrimination about the subsequent sheets.
In Japanese Patent Application Laid-Open No. 2007-055814, by using such a sheet type discriminating method, the types of a predetermined number of sheets are detected, discriminated, and decided, and a sheet type discrimination result is stored every sheet feed port. After the sheet types were discriminated, in a print job which is printed after the sheet types were decided, control is made based on the discrimination results (sheet types) which have previously been stored. By using such a method, a deterioration in throughput that is caused by the sheet type discriminating process is reduced.